E-mail: ihrsak@olimp.irb.hr
Summary: In the years 1994. and 1995. investigations of the
mechanism of action of biological response modifiers, i.e. bacterial
peptidolgycans (PGM) and met-enkephalin (MENK) have been continued. PGM
and its lipophylic derivative Na-lauroil-PGM stimulate macrophageas from
the spleen and RAW 264.7 cultures to release increased quantities of TNF.
Metalo-derivatives of PGM (Zn-PGM and Al-PGM) as well as lipophylic
derivative Na-lauroil-PGM are not effective. PGM and LPS added to the
macrophages in suboptimal doses does not induce synergistic effect on TNF
release. In vivo single injection of PGM changed temporarily the
permeability of liver lysosomal membranes and increased the quantity of
lipid peroxidation products in plasma and liver. In vitro administration
of PGM modulated macrophage superoxide anion production but did not affect
the activity of lysosomal membrane and enzymes. In vitro multiple
injections of PGM did not cause significant changes in the examined
parameters. In animals subjected to stress the intensity of lipid
peroxidation and corticosterone levels in the sera could be modulated by
the treatment with MENK. The in vitro effects of lipophylic and metalo
PGM-derivatives on the metabolic activity of spleen macrophages in
preleukemic AKR mice have been tested and the results obtained compared to
the effects of native PGM. In the 1 month young mice neither PGM nor their
derivatives had any effect. On the contrary, in young-adult (4 month old)
mice PGM and some of its derivatives stimulated the depressed activity of
mitochondrial enzymes. Stimulation of superoxide anion release by MENK is
associated with an increse of diacylglycerol, translocation of protein
kinase C into the membranes of treated cells and an increase of
intracellular calcium. The main degradating product of MENK (TGG),
suppressed superoxide anion release, and this was not associated with the
increased levels of diacylglycerol. In vivo MENK affected the immune
response like in the stress; NK activity and antibody production were
decreased, phagocytosis enhanced and the level of corticosterone elevated.
If the MENK is applied before stressing the animals, then the effects of
stress could be blocked, what suggests the involvement of
hypothalamo-pituitary-adrenal axis in the mechanism of opioid effects.

Research goals: The aims of the investigations in this project are
to get better knowledge about the mechanisms of action of biological
response modifiers - peptidoglycans and met-enkephaline on the cellular
and subcellular levels. In the years 1994. and 1995. the aim was to
investigate whether some lypophilic and metalo-derivatives of
peptidoglycan PGM have better or different effect than the native PGM, as
well as whether this biological response modifiers have possible unwanted
toxic side effects on metabolic functions of liver and splenic cells in
physiological and stress-induced states. In the same conditions we wanted
to examine the mechanism of MENK effect upon several immune functions (NK
activity, phagocytosis, antibody production, blastogeneic transformation)
and the level of corticosterone in the plasma of stressed mice. Also, it
was planed to examine which second messenger(s) is involved in MENK
induced production of superoxide anion from human neutrophils.